Synchronization of ovulation in crossbred dairy heifers using gonadotrophin-releasing hormone agonist, prostaglandin F2a and human chorionic gonadotrophin or estradiol benzoate

Girolando (Gir x Holstein) is a very common dairy breed in Brazil because it combines the rusticity of Gir (Bos indicus) with the high milk yield of Holstein (Bos taurus). The ovarian follicular dynamics and hormonal treatments for synchronization of ovulation and timed artificial insemination were studied in Girolando heifers. The injection of a gonadotrophin-releasing hormone (GnRH) agonist was followed 6 or 7 days (d) later by prostaglandin F2a (PGF2a). Twenty-four hours after PGF2a injection either human chorionic gonadotropin (hCG, GPh-d6 and GPh-d7 groups) or estradiol benzoate (EB, GPE-d6 and GPE-d7 groups) was administered to synchronize ovulation and consequently allow timed artificial insemination (AI) 24 and 30 h after hCG and EB injection, respectively. Follicular dynamics in Girolando heifers was characterized by the predominance of three follicular waves (71.4%) with sizes of dominant follicles (10-13 mm) and corpus luteum (approximately 20 mm) similar to those for Bos indicus cattle. In the GnRH-PGF-hCG protocol, hCG administration induced earlier ovulation (67.4 h, P<0.01) compared to the control group (GnRH-PGF) and a better synchronization of ovulation, since most of it occurred within a period of 12 to 17 h. Pregnancy rate after timed AI was 42.8 (3/7, GPh-d6) to 50% (7/14, GPh-d7). In contrast, estradiol benzoate (GnRH-PGF-EB protocol) synchronized ovulation of only 5 of 11 heifers from the GPE-d7 group and of none (0/7) from the GPE-d6 group, which led to low pregnancy rates after timed AI (27.3 and 0%, respectively). However, since a small number of Girolando heifers was used to determine pregnancy rates in the present study, pregnancy rates should be confirmed with a larger number of animals.

Effect of follicle size on mRNA expression in cumulus cells and oocytes of Bos indicus: an approach to identify marker genes for developmental competence

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Influence of cage fish farming on the diet of dominant fish species of a Brazilian reservoir (Tiete River, High Parana River basin)

The cage farming of aquatic organisms was initiated 50 years ago, and was introduced to Brazil in the 1990's. In these systems, there is an input of organic matter from ration that is not totally used by the cage fishes, becoming available for the organisms of adjacent biota, including fish fauna. The aim of this work is to evaluate the interference in the diet of three dominant fish species (Plagioscion squamosissimus Heckel, 1840, Astyanax altiparanae Garutti and Britski, 2000 and Metynnis maculatus Kner, 1858) associated with ish cage farming. For determination of the diet, the Alimentary Index (AI) was used. In both stretches (around cage farm and control), P. squamosissimus selected aquatic insects, while A. altiparanae preferred terrestrial insects and M. maculatus eats ration remains. Diferences in abundance of these feeding resources found of the stomach content were observed among the two stretches. Thus, the small alterations in the diets of P. squamosissimus and A. altiparanae, indicate that cage farming can change the diet of resident species in reservoirs. This practice also influences the population structure of fish species, since higher middle standard lengths were found in A. altiparanae and P. squamosissimus populations resident around cage farms, in relation to the control stretch.

Follicle profile and plasma gonadotropin concentration in pubertal female ponies

Twelve female ponies were examined daily for 30 days and classified as ovulating (OV; N = 6; 197 ± 6 kg) or prepubertal (PP; N = 6; 196 ± 9 kg). Follicles were detected by ultrasound and gonadotropins quantified by radioimmunoassay. The mean diameter of the largest follicles was significantly larger in OV (38 ± 1 mm) than in PP (26 ± 2 mm) but there was no difference between groups in the size of the second largest follicle. There were more small follicles (<24 mm) in the PP than in the OV group, but PP fillies had a smaller number of follicles >29 mm than the OV fillies. Follicle-stimulating hormone (FSH) levels did not differ between groups but PP fillies had lower luteinizing hormone (LH) peak (8 ± 1 ng/ml) and basal (4 ± 0.5 ng/ml) levels, lower peak magnitude (2 ± 0.2 ng/ml) and period average (5 ± 0.6 ng/ml) than OV fillies (32 ± 4.5, 8 ± 1.2, 17.1 ± 6, and 15 ± 2.3 ng/ml, respectively). The PP group, in contrast to the OV group, showed no relationship between FSH surge and follicle wave emergence. We conclude that an LH concentration higher than 8 ng/ml is needed for follicle growth to a preovulatory size. Wave emergence and FSH secretion seem to be independent events, probably due to an inhibitory neural system in these PP animals. PP fillies may provide a physiological model for the study of follicle wave emergence which apparently does not depend on gonadotropin levels.

Estimation of outcrossing rate in a breeding population of Eucalyptus urophylla with dominant RAPD and AFLP markers

Eucalyptus breeding is typically conducted by selection in open-pollinated progenies. As mating is controlled only on the female side of the cross, knowledge of outcrossing versus selling rates is essential for maintaining adequate levels of genetic variability for continuous gains. Outcrossing rate in an open-pollinated breeding population of Eucalyptus urophylla was estimated by two PCR-based dominant marker technologies, RAPD and AFLP, using 11 open-pollinated progeny arrays of 24 individuals. Estimated outcrossing rates indicate predominant outcrossing and suggest maintenance of adequate genetic variability within families. The multilcous outcrossing rate (t(m)) estimated from RAPD markers (0.93 +/- 0.027), although in the same range, was higher (alpha > 0.01) than the estimate based on AFLP (0.89 +/- 0.033). Both estimates were of similar magnitude to those estimated for natural populations using isozymes. The estimated Wright's fixation index was lower than expected based on t, possibly resulting from selection against selfed seedlings when sampling plants for the study. An empirical analysis suggests that 18 is the minimum number of dominant marker loci necessary to achieve robust estimates of t,. This study demonstrates the usefulness of dominant markers, both RAPD and AFLP, for estimating the outcrossing rate in breeding and natural populations of forest trees. We anticipate an increasing use of such PCR-based technologies in mating-system studies, in view of their high throughput and universality of the reagents, particularly for species where isozyme systems have not yet been optimized.

A new locus for autosomal dominant amelogenesis imperfecta on chromosome 8q24.3

Amelogenesis imperfecta (AI) is a collective term used to describe phenotypically diverse forms of defective tooth enamel development. AI has been reported to exhibit a variety of inheritance patterns, and several loci have been identified that are associated with AI. We have performed a genome-wide scan in a large Brazilian family segregating an autosomal dominant form of AI and mapped a novel locus to 8q24.3. A maximum multipoint LOD score of 7.5 was obtained at marker D8S2334 (146,101,309 bp). The disease locus lies in a 1.9 cM (2.1 Mb) region according to the Rutgers Combined Linkage-Physical map, between a VNTR marker (at 143,988,705 bp) and the telomere (146,274,826 bp). Ten candidate genes were identified based on gene ontology and microarray-facilitated gene selection using the expression of murine orthologues in dental tissue, and examined for the presence of a mutation. However, no causative mutation was identified.

Reduction in size of the ovulatory follicle reduces subsequent luteal size and pregnancy rate

We hypothesized that reducing the size of the ovulatory follicle using aspiration and GnRH would reduce the size of the resulting CL, reduce circulating progesterone concentrations, and alter conception rates. Lactating dairy cows (n=52) had synchronized ovulation and AI by treating with GnRH and PGF(2 alpha) as follows: Day -9, GnRH (100 mug); Day -2, PGF(2 alpha) (25 mg); Day 0, GnRH (100 mug); Day 1, AI. Treated cows (aspirated group; n=29) had all follicles > 4 mm in diameter aspirated on Days -5 or -6 in order to start a new follicular wave. Control cows (nonaspirated group; n=23) had no follicle aspiration. The size of follicles and CL were monitored by ultrasonography. The synchronized ovulation rate (ovulation rate to second GnRH injection; 42/52=80.8%) and double ovulation rate of synchronized cows (6/42=14.3%) did not differ (P > 0.05) between groups. Aspiration reduced the size of the ovulatory follicle (P < 0.0001; 11.5 +/- 0.2 vs 14.5 +/- 0.4 mm), and serum estradiol concentrations at second GnRH treatment (P < 0.0002; 2.5 +/- 0.4 vs 5.7 +/- 0.6 pg/mL). The volume of CL was less (P < 0.05) for aspirated than nonaspirated cows on Day 7 (2,862 +/- 228 vs 5,363 +/- 342 mm(3)) or Day 14 (4,652 +/- 283 vs 6,526 +/- 373 mm(3)). Similarly, serum progesterone concentrations were less on Day 7 (P < 0.05) and Day 14 (P < 0.10) for aspirated cows. Pregnancy rate per AI for synchronized cows was lower (P < 0.05) for aspirated (3/21=14.3%) than nonaspirated (10/21=47.6%) cows. In conclusion, ovulation of smaller follicles produced lowered fertility possibly because development of smaller CL decreased circulating progesterone concentrations. (C) 2001 by Elsevier B.V.

Synchronization rate, size of the ovulatory follicle, and pregnancy rate after synchronization of ovulation beginning on different days of the estrous cycle in lactating dairy cows

Recently a protocol was developed that precisely synchronizes the time of ovulation in lactating dairy cows (Ovsynch; GnRH-7d-PGF(2 alpha)-2d-GnRH). We evaluated whether initiation of Ovsynch on different days of the estrous cycle altered the effectiveness of this protocol. The percentage of cows (n=156) ovulating to the first GnRH was 64% and varied (P<0.01) by stage of estrous cycle. Treatment with PGF(2 alpha) was effective, with 93% of cows having low progesterone at second GnRH. The overall percentage of cows that ovulated after second GnRH (synchronization rate) was 87% and varied by response to first GnRH (92% if ovulation to first GnRH vs 79% if no ovulation; P<0.05). There were 6% of cows that ovulated before the second injection of GnRH and 7% with no detectable ovulation by 48 h after second GnRH. Maximal diameter of the ovulatory follicle varied by stage of estrous cycle, with cows in which Ovsynch was initiated at midcycle having the smallest follicles. In addition, milk production and serum progesterone concentration on the day of PGF(2 alpha) affected (P<0.05) size of the ovulatory follicle. Using these results we analyzed pregnancy rate at Days 28 and 98 after Al for cows (n=404) in which Ovsynch was initiated on known days of the estrous cycle. Pregnancy rate was lower for cows expected to ovulate larger follicles than those expected to ovulate smaller follicles (P<0.05; 32 vs 42%). Thus, although overall synchronization rate with Ovsynch was above, 85%, there were clear differences in response according to day of protocol initiation. Cows in which Ovsynch was initiated near midcycle had smaller ovulatory follicles and greater pregnancy rates. (C) 1999 by Elsevier B.V.

Ovulation synchronization following commercial application of ultrasound-guided follicle ablation during the estrous cycle in mares

A regimen of progesterone plus estradiol (P&E) was used as a standard for ovarian synchronization to test the efficacy and evaluate the commercial application of ultrasound-guided follicle ablation as a non-steroidal alternative for ovulation synchronization in mares. Recipient mares at a private embryo transfer facility were at unknown stages of the estrous cycle at the start of the experiment on Day 1 when they were randomly assigned to an ablation group (n = 18-21 mares) or to a ME group (n = 20-21 mares). In the ablation group, mares were lightly sedated and all follicles > 10 mm were removed by transvaginal ultrasound-guided follicle aspiration. In the ME group, a combination of progesterone (150 mg) plus estradiol (10 mg) prepared in safflower oil was given daily (im) for 10 d. Two doses of prostaglandin FZ, (PGF, 10 mg/dose, im) were given 12 h apart on Day 5 in the ablation group, or a single dose on Day 10 in the ME group. Human chorionic gonadotropin (hCG, 2500 IU/mare, im) was given at a fixed time, 6 and 10 d after PGF treatment in the ablation and ME groups, respectively, with the expectation of a follicle > 30 mm at the time of treatment. In both the ablation and P&E groups, transrectal ultrasonography was done at the start of the study (Day 1) and again on the day of hCG treatment and daily thereafter to determine the presence of a CL, measure diameter of the largest follicle and detect ovulation. The mean interval from the start of the study and from PGF treatment to ovulation was shorter (P < 0.0001) in the ablation group (13.7 and 9.7 d, respectively) compared to the P&E group (22.3 and 13.2 d, respectively). Following fixed-day treatment with hCG after PGF treatment, the degree of ovulation synchronization was not different (P > 0.05) between the ablation and P&E groups within a 2-d (56 and 70%) or 4-d (83% and 90%) period. Although ultrasound-guided follicle ablation may not be practical in all circumstances, it excluded the conventional 10-d regimen of progesterone and estradiol and was considered an efficacious and feasible, non-steroidal alternative for ovulation synchronization in mares during the estrous cycle. (C 2007 Elsevier B.V. All rights reserved.

Differential response of the luteal phase and fertility in cattle following ovulation of the first-wave follicle with human chorionic gonadotropin or an agonist of gonadotropin-releasing hormone

A series of experiments with Holstein heifers was conducted to develop the capability of inducing accessory corpus luteum (CL) with a GnRH agonist (Buserelin, 8 mu g; GnRHa) or hCG; (3,000 IU) to increase plasma progesterone concentrations (Exp. 1, 2, and 3) and to test whether induction of accessory CL with hCG will increase conception rates in heifers (Exp. 4) and lactating cows (Exp. 5). In Exp. 1, heifers were treated on d 5 after estrus with GnRHa (n = 8) or saline (n = 7); heifers in Exp. 2 received hCG (n = 5) or saline (n = 4) on d 5. Experiment 3 allowed a contemporary evaluation of heifers treated on d 5 with GnRHa (n = 6), hCG (n = 6), saline (n = 6), or GnRHa at d 5 and hCG at the time of the induced ovulation (n = 5). The GnRHa and hCG were equally effective in inducing an accessory CL (93% induction rate), but the subsequent increase in progesterone concentrations was greater in hCG-treated heifers. A greater half life of hCG may provide longer LH-like stimulation of the first-wave follicle and subsequent developing accessory CL or a greater luteotropic effect on the original CL. Induction of an accessory CL with hCG on d 5 or 6 after insemination did not increase pregnancy rates in fertile heifers (Exp. 4: hCG = 64.8% vs control = 62.9%; n = 243) or lactating dairy cows during summer heat stress (Exp. 5: hCG = 24.2% vs control = 23.5%; n = 201).

Ovarian follicle diameter at timed insemination and estrous response influence likelihood of ovulation and pregnancy after estrous synchronization with progesterone or progestin-based protocols in suckled Bos indicus cows

The objectives of the present study were to evaluate factors associated with estrous synchronization responses and pregnancy per insemination (P/AI) in Bos indicus beef cows submitted to progesterone-based fixed-time artificial insemination (FTAI) protocols. A total of 2388 cows (1869 Nellore and 519 crossbred Nellore x Angus) from 10 commercial farms were evaluated to determine the relationships among breed, body condition score (BCS) on the first day of the FTAI protocol, the occurrence of estrus between progesterone device removal and FTAI and diameter of largest ovarian follicle (LF) at FTAI on estrous synchronization responses and P/AI. Cows (n=412 primiparous; 1976 multiparous) received an intravaginal device containing progesterone or an ear implant containing norgestomet (a progestin), and an injection of estradiol at the beginning of the estrous synchronization protocol. Body condition was scored using a 1-5 scale on the first day of the FTAI protocol and at 30-60 days postpartum. Females received 300IU of equine chorionic gonadotropin (eCG) and PGF(2 alpha) on the day the progesterone device/implant was removed and were inseminated 48-60h later. At insemination, cows (n=2388) were submitted to an ultrasonographic exam to determine the diameter of the LF. Follicles were classified into four categories based on mean and standard deviation (SD) of the LF (LF1 = two SD below the mean; LF2 = mean minus one SD; LF3 = mean plus one SD; LF4 = two SD above the mean). Ovulation rate was determined in a subset of cows (n=813) by three consecutive ultrasonographic exams: (1) at time of progesterone device/implant removal, (2) at time of FTAI and (3) 48 h after FTAI. Ovulation was defined as the disappearance of a large follicle (>= 8.0 mm) that was previously recorded. Estrus was determined in a subset of the cows (n = 445) by the activation of a detection of estrous patch placed on the tail head on the day of progesterone device/implant removal. Pregnancy was diagnosed 30 days after FTAI. Pregnancy was influenced (P = 0.001) by follicle diameter [LF1 = 27.5% (81/295), LF2 = 46.6% (328/705), LF3 = 57.9% (647/1118), LF4 = 63.3% (171/270)] and the occurrence of estrus [estrus = 67.7% (174/257) and no estrus = 36.2% (68/188)]. Follicle diameter at FTAI influenced ovulation rate [LF1 = 42.5% (34/80), LF2 = 73.9% (161/218), LF3 = 95.8% (407/425), LF4 = 97.8% (88/90)], the occurrence of estrus [LF1 = 54.8% (51/93), LF2 = 33.6% (43/128), LF3 = 68.9% (126/183), LF4 = 90.2% (37/41)] and P/AI among cows that had ovulations [LF1 =32.4% (11/34), LF2 = 50.3% (81/161), LF3 = 60.0% (244/407), LF4 = 68.2% (60/88)]. Improving estrous responses between progesterone device withdrawal and FTAI and increasing the diameter of the LF at FTAI may be important aspects to achieve improved estrous synchronization responses and P/AI following progesterone/progestin and estradiol based FTAI protocols in suckled Bos indicus cows. (C) 2010 Elsevier B.V. All rights reserved.